Halo of the Cat's Eye
Credit:
R. Corradi (Isaac Newton Group),
D. Goncalves (Inst. Astrofisica
de Canarias)
The Cat's Eye Nebula
(NGC 6543) is one of the best known planetary
nebulae in the sky.
Its haunting symmetries are seen in the very central region
of this stunning false-color picture, processed to reveal the
enormous but extremely faint halo of gaseous material, over three
light-years across, which surrounds the brighter,
familiar planetary nebula.
Made with data from the
Nordic Optical Telescope
in the Canary Islands, the composite picture
shows emission from
nitrogen atoms as red and oxygen atoms as green and blue shades.
Planetary
nebulae have long been appreciated as a final phase
in the life of a sun-like star.
Only much more recently however, have some planetaries been
found to have halos
like this one, likely formed of material shrugged off during
earlier active episodes in the star's evolution.
While the planetary
nebula phase is thought to last for around 10,000 years,
astronomers estimate the age of the outer filamentary portions
of this halo to be 50,000 to 90,000 years.